Tuesday December 24, 2013, 8:53 pm
The sequencing results, published today in the journal Nature, also reveal Neanderthals, early modern humans and a sister group to Neanderthals, Denisovans, met and reproduced in the Late Pleistocene between 12,000 and 126,000 years ago.

Alan Cooper, a professor at the Australian Centre for Ancient DNA at the University of Adelaide, says the study "completely rewrites what we know about human evolutionary history".

"We now have a reasonably definitive picture of the mixing and matching of [hominin] groups through time," he says.

And according to Cooper, the research reveals that "everyone is bonking everyone else … it's quite impressive".

First author of the paper Kay Prufer, of the Max Planck Institute for Evolutionary Anthropology in Germany says the findings are based on DNA extracted from a toe bone found in the Siberian cave where the first Denisovan fossils were discovered in 2008.

The toe bone belonged to a Neanderthal woman who they estimate lived about 50,000 years ago, he says, adding that DNA analysis shows the woman's parents were very closely related.

"We conclude the parents of this Neanderthal individual were either half-siblings who had a mother in common, double first cousins, an uncle and a niece, an aunt and a nephew, a grandfather and a granddaughter, or a grandmother and a grandson," the researchers write.

Prufer says the analysis shows this inbreeding was not a rare event.

"The parents were very closely related, but even if you ignore that [DNA analysis shows] … the past parents of the parents were related," he says.

Prufer says the inbreeding suggests the Neanderthal population was quite small or fragmented and this may have played into their demise.

"Of course if you have a small population size you begin to move into the danger zone [for extinction]," says Prufer.

Cooper, who was not involved in the study, agrees: "If you are breeding with your uncle, your population is on the way out. The fact this group has been doing it for a while suggests it was in decline."

As part of the study, the international team also compared genomes of Neanderthals, Denisovans and modern-day humans.

Previous research has shown that while Neanderthals contributed to the genetic heritage of all modern populations outside Africa, Denisovans contributed exclusively to populations in Southeast Asia and Oceania.

However Prufer says the analysis reveals the picture may be more complex.

Their study shows gene flow from Neanderthals to Denisovans indicating interbreeding between the two groups.

The Denisovan DNA also contained genetic material from an "unknown archaic human that lived a million years ago", says Prufer.

He says this "unknown archaic human" could be Homo erectus, but further analysis is needed to determine its origins.

Prufer says by comparing the genome of the various hominin groups, researchers will also be able to pinpoint the "defining changes" in genome that genetically make modern humans.

Their work suggests the proportion of Neanderthal-derived DNA in all people outside Africa is about 1.5 to 2.5 per cent.

Cooper says the findings show evolution works in a "complicated and messy fashion".

"And when you try and reconstruct evolutionary history by looking at modern genetic data you get it completely wrong," he says.

While the work is "very convincing" Cooper says it is unlikely to be the final version of evolution.

"Five years ago we didn't even know of the existence of the Denisovans," he says.

"It is an incremental process [but] these discoveries are really changing how we think about human evolution."

Cooper says the sequencing of the genomes also opens up the possibility to "identify what bits of Neanderthal and Denisovan DNA survive in us and what they might be doing".

Wednesday December 25, 2013, 7:20 am
Okay so if i understand correctly---we are all basically inbred? Not very comforting. If this holds true well we're even more stupid then i thought. The Monarchies through the centuries are very familiar with inbreeding. These noble nut heads practically coined the term! Thx Michael

Wednesday December 25, 2013, 4:17 pm
all the kings and queens of Europe were cousins and the original settlers in Canada and the USA often married cousins I am not supportive of incest, but it happens every day. it wouldn't have been made a sin or illegal if it wasn't common

Wednesday December 25, 2013, 11:30 pm
30 to 40 years ago, the scientific community were sure that modern humans (Homo sapiens) and Neanderthals had never interbred, and that Neanderthal DNA had died out: I never believed that, and I'm happy to have been proved right (gloating grin).

I wonder if the evidence of interbreeding was a symptom of Neanderthal population decline, or a causal factor -- hmm?

Thursday December 26, 2013, 7:15 am
Not much new under the sun it seems, speaking behavior that is.

Knowing this part of our history it's even more shocking that at this very moment, even if there's only one species, Homo Sapiens Sapiens, left, there still are people who think it's not good to have children (or even live with) people having another color of skin, form of nose, eyes, mouth etc.

Thursday December 26, 2013, 7:58 pm
That very tiny group likely went extinct, so the comment that our ancestors inbred does not fit.
"Prufer says the inbreeding suggests the Neanderthal population was quite small or fragmented and this may have played into their demise.

"Of course if you have a small population size you begin to move into the danger zone [for extinction]," says Prufer."

Thursday December 26, 2013, 9:42 pm
Thanks so much for posting Michael. Like Maureen, I never went with mainstream thought over the past decades about no interbreeding between Neanderthals and Homo Sapiens Sapiens, mainly because of the Skhul/Qafzeh hominid findings (in modern-day Israel) that exhibit both archaic and modern anatomical traits. I was very happy when genetic analyses proved interbreeding beyond doubt. I have read elsewhere that the proportion of Neanderthal-derived DNA in living humans may be as high as 4% and that it is associated with immune system hardiness. It isn't surprising that small, fragmented hominin populations were incestuous. The same thing is happening today in animal populations that have been hunted to near extinction or where habitat has been grossly destroyed or segmented by human development. This is why zoos fly various animals from one country to another to promote gene diversity. Diversity occurs naturally when any population of creatures have access to unrelated mates. Some cultures have promoted incest amongst nobility to ensure that land and wealth remained within certain families or clans, but this was not the norm of any large population. The story of human evolution is not a simple one. With more fossil finds and enhanced techniques for working with ancient DNA we are coming to discover new and more complex information about our ancestry and I find it really exciting.

Friday December 27, 2013, 2:46 am
Perhaps a way for genes and species to alter, genetic modification is called mutation, a permanent transmissible change in the genetic material. Also, an individual exhibiting such change; a sport.